Do https://support.mozilla.org/en-US/kb/profiling-thunderbird-performance and PM me the profile link or file.

Thanks for the answer. I still had the problem with my TB 143 profile last friday. After 7 mails sent it took 30 seconds to send mails. Today I set up the profiling parameters and tested more than 50 mails with no problem. I'll check further today and start the recording if problem occurs again

Th

Hi again as soon I wrote the message the problem occured agan. More than 1 minute and ficnished with timeout to the mail server. Juste resent it and worked as expected. When finishing the record session I got en arror message in attached screen shot.

Restarted the process with daily 145.0a1 (2025-10-12) (64 bits) I soon had the problem of slow sending, ending with a timeout. The link of the capture is: https://share.firefox.dev/3WzgKkl

Thanks for help

Restarted the process with daily 145.0a1 (2025-10-12) (64 bits) I soon had the problem of slow sending, ending with a timeout. The link of the capture is: https://share.firefox.dev/3WzgKkl

Thanks for help

Are you using pop accounts? Or imap accounts?

Also, what happens if you disable the send progress?

Settings > General > Config Editor > paste in mailnews.show_send_progress > change it to false

Hi, I am using IMAP (with SSL) With mailnews.show_send_progress option to false, it took 24 seconds to send the mail and give me back a hand

Received: from [134.158.18.50] (marmth.in2p3.fr [134.158.18.50]) (authenticated bits=0) by cczrelay02.in2p3.fr (8.14.4/8.14.4) with ESMTP id 59FEwPrM012104 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NO) for <mouthuy@cppm.in2p3.fr>; Wed, 15 Oct 2025 16:58:48 +0200 Message-ID: <c49834c8-efc6-4bad-8cb1-274820cfaca7@cppm.in2p3.fr> Date: Wed, 15 Oct 2025 16:58:24 +020

@mouthuy,

Question from the developers - does the slowness OR high memory still occur if you use a current Daily or 145.0b2 (after bug 1994411)?

Sorry I was out of business for few days. I download 146.0a1 The 6 first messages were sent immediately. The number 7 took 7 seconds and the number 8, 25 seconds. So I guess problem is still there

I wouldn't expect it to help, but does settings preference accessibility.force_disabled to value 1 help?

No this does not change anything. The 5 first mails go fast, and the 6th one took 30 seconds.

No this does not change anything. The 5 first mails go fast, and the 6th one took 30 seconds.

Same here, it started when I upgraded to 144.01 from my previous version of about 140.0 Very slow and some timeouts

Hopefully later versions will work better, I'll try a beta release and see if it's better I'm also using I am using IMAP (with SSL)

Was always super fast till the upgrade Other than that it's all good !

This might be a google mail issue - if you post an update, may I suggest you mention if it is a google imap account or some other imap account

Hi The Imap account that causes problem is my institutional ZIMBRA account. Zimbra version 10.1.13_GA_4837.NETWORK. I do have more and more colleagues which are using a more recent version than the 140ESR and fall in the same trap.

Hi TB 145 became official in Fedora distrib.

After may tests, I found out that browser.cache.disk_cache_ssl was true in my profile. I changed it to false, and I could send a sequence of 15 mails without significant delay/timeout (before I had 30 sec to 60 sec delay after the 6th mail). Other colleagues seem to have the same problem (including on Mac OS). I'll continue testing with them.

Unfortunately the previous message is wrong. A new session causes approx delays of 3 to 5 seconds till mail number 6. The seventh took 53 seconds. Sorry for noise

147 comes out this week in a couple days at https://www.thunderbird.net/en-US/download/. Or, are you using beta?

Hello I download 147 and started from scratch with a new profile. Mails 1 to 5 went immediatly through SMTP server. Mail nb 6 took 10 seconds, nb 7 took 52 seconds, next one 34 seconds

I may mention more people are using 146 as it became standard in Fedora and exhibit the same problem. Some colleagues on MAC are also using 146 and have the same problem.

It is certaintely relate to a change in TB and a problem with our version (institutionnal) of Zimbra. But up to now no one could understand the origin and the solution

I appreciate you sharing these details; this is very useful.